Electrostatic paint spray



Oct. 17, 1961 H. J. REINDL 3,004,517

ELECTROSTATIC PAINT SPRAY Filed April 4, 1958 2 Sheets-Sheet -1 l9 [If INVENTOR.

| lI-IIIIII Harold J. Re/nd/ F/g. P- M His Attorney Oct. 17, 1961 Filed April 4, 1958 H. J. REINDL ELECTROSTATIC PAINT SPRAY 2 Sheets-Sheet 2 Fig.3

I I INVENTOR.

Harold J. Re/nd/ His Attorney United States Patent 3,004,517 ELECTROSTATIC PAINT SPRAY Harold J. Reindl, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaare Filed Apr. 4,1958, Ser. No. 726,449 9 Claims. (Cl. 118-627) This invention relates to an electrostatic paint spray apparatus and is particularly concerned with a centrifugal type of electrostatic paint spray apparatus.

It is one of the objects of the invention to provide a rotating or centrifugal type of electrostatic paint spray apparatus wherein the centrifugal distribution of the paint is caused by rotation of the paint distributing device around two axes spaced 90 from one another.

Another object of the invention is to provide an electrostatic paint spray apparatus utilizing a centrifugal distributor wherein the distributor comprises an open-ended tubular spray head which rotates in an orbit around a center and wherein the spray head also rotates about its axis.

. Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a plan view, in perspective, of the distributing head showing paint being emitted therefrom onto an article to be painted carried by a conveyor spaced from the head.

FIGURE 2 is a top view, not to scale and partially cut away, of the distributor head shown in FIGURE 1.

FIGURE 3 is a sectional view of the distributor head shown in FIGURE 1.

FIGURE 4 is a plan view showing the distributor in the center of a' conveyor system whereby articles conveyed in a path around the distributor are painted thereby.

Electrostatic paint spray equipment is well known in the art and various types of paint distributors have been proposed. One of these distributors is shown in my copending application, S.N. 687,107, wherein a rotating blade is used to distribute paint centrifugally to form an undulating circular pattern which may be used to paint a plurality of articles passing around the distributor on a conveyor of any specific shape. In this instance, the conveyor may bercircular or may be of a non-rectilinear design as shown in my copending application, S.N. 698,490, now Patent No. 2,947,281, one design 18 being shown here in FIGURE 4.

One of the important factors in electrostatic spray painting is to control the pattern of painting so that the 'paint is directed and restricted in the field where it is to be used. This eliminates over-spray and, even when electrostatic forces are utilized, if the over-spray is substantial, it is impossible to obtain full control whereby paint is wasted since it is not fully attracted to the article or articles being painted. Therefore, it is of considerable importance to be able to control the shape of the paint pattern and, in this connection, it is highly desirable to, when painting is an expanding circular pattern in one plane, fully control the height of said pattern whereby the height of the pattern is maintained substantially the same as the height of the article or articles being painted.

The present invention is directed to distributing apparatus which may be used to provide a generally expanding pattern of paint in a circular path wherein the height of said pattern may be controlled by utilizing a tubular type centrifugal spray head or emitter which is rotated simultaneously in two planes. Referring specifically to the drawings, such a distributor is shown at 20 in FIGURE 1 and comprises a base plate 22 suitably supported by a base 19 and a stationary central shaft 24. The shaft 24 is preferably insulated from plate 22 and the base 20 is insulated from the plate 22. Also carried on the plate 2: is an annular beveled gear 26 bolted thereto by bolts A central housing member 30 supports a pair of opposed bearings 32 which carry tubular emitter members or spray heads 34. The emitters 34 are preferably coned inwardly at the ends thereof to form restricted throats 36 and have beveled gears 38 fixed thereto around their external surfaces which gears 38 are adapted to mesh with the gear 26. The emitters 34 are rotatable through a sliding connection on a central T-shaped tubular member 40 which is joined with the housing 30 for the shaft 24. The housing 30 is attached to an air or electric motor (not shown) which is capable of rotating the housing 30, emitters 34 and related parts. The housing 30 carries a paint supply cup 50 on the upper portion which is rotatable therewith. The cup 50 connects by means of tubes 52 with the emitters 34 wherein the tubes are used to supply paint to the internal surfaces of the emitters. The cup 5% is supplied paint from an external source by a single stationary paint supply tube 60. Thus, paint supplied to the cup 50 will pass through both tubes 52 and thence to the emitters 34.

When the motor, not shown, causes the member 30 to rotate, the emitters 34 will rotate about their axes due to the fact that plate 22 and gear 26 are stationary while gears 38 are rotating in an orbit about the central shaft 24. Thus, while the emitters 34 are rotating around their axes, they are also rotating in an orbit around the shaft 24. When paint is supplied through the tube 60, cup 50 and tubes 52, it flows onto the lower surfaces of the emitters and is centrifugally distributed therearound by the axial rotation of the emitters. Simultaneously, it is centrifugally distributed outwardly of the emitters by the orbital rotation of the emitters whereby it is thrown from the constricted throats 36 of the emitters in a relatively narrow band as controlled, to a large degree, by the diameter of the throats 36.

In operation, the emitters 34 are connected to one pole of an electrostatic circuit by a wire 64 connected to an electrostatic power unit 66. The other pole of the circuit is connected by wire 68 to a conveyor 70 which carries an article or articles 72 to be painted. Thus, paint, which is centrifugally distributed, as shown in dash lines on FIGURE 1, by the emitters, simultaneously is charged as it leaves the throats 36 of the emitters and is electrostaticaly broken up further into a fine mist of charged particles which are attracted to the article or articles 72 due to the fact that these articles carry an opposite charge. In this manner, it is possible to provide a narrow band of an expanding circular nature of charged paint particles which band is substantially the height of the article or articles to be painted.

Different width bands may be obtained by merely changing the throat diameters, that is, by dropping the plate 22 and removing the emitters with their gears and bearings and replacing them with other and different diameter emitter units. It is possible, likewise, to utilize one emitter together with a dummy emitter on the opposite side to provide contrifugal balance or it is possible to utilize opposed emitters or three, four, five or any number of emitters as desired. In practice, two emitters yield highly satisfactory results. although this invention by as the device rotates, the pattern Will actually take on a scalloped shape with respect to height since, as the 3 emitters rotate around the orbit and pass a given point, the height of pattern will vary in accordance with the diarneter of the emitter passing said point.

Aspecific example of the invention is as follows: Two opposed emitters, as shown in FIGURE 3, each' having a threeand one-half inch diameter and'four inch length, and having throats of three inch diarrreter, were each fed paint at a point three inches from said throats; The ernitters were carried by a housing rotating at a speed or 200 r.p.m. and the throats of the emitters were spaced thirtysix inches apart. The emitters were rotated about their longitudinal axes at about 3000 r.p.m. by means of snitable gearing. This yielded an expanding circular paint pattern which had a height of about eighteen inches on an article positioned twenty-four inches from the throats or around a circular path having a seven foot diameter with respect to the center of the apparatus. An electrostatic charge of 100,00volts between the emitters and the articles to be painted yielded satisfactory results. I s v Emitters having a two-inch diameter throat, used under similar conditions, reduced the height of pattern to about twelve inches.

Still another example using substantially the same physical equipmentutilizes an orbital rotation of from 2,0' to 2.5 r.p.m. and an axial rotation of the emitters of about 9 00 r.p.m. An electrostatic charge of about 120,- 000" volts was used with an emitter throat size of one inch.

surface of the spray head and is centrifugally thrown outwardly from the other end' of said head.

4. In a paint spray apparatus, a horizontal stationary plate including a ring gear therearound, a horizontal tubular spray device, mechanical driving means for rotating said device in an orbit,- a gear on said tubular spray device adapted tomesh with sa'id ring gear for causing the spray device to simultaneously rotate about its horizontal axis during rotation in said orbit, and feeding means for supplying paint toth'e internal tubular surface of the spray device, whereby the paint is centrifugally distributed upon said tubular surface and is centrifugally expelled' from said device in an expanding circular pattern.

5. An electrostatic paint spray apparatus, comprising in combination; an electrostatic power pack having one pole thereof attached to an article tobe painted, an electrostatic paint distributor-connected to the other pole of the power pack and spaced a predeterrnined distance from said article to be painted, said distributor including a tubular emitter element having a restricted throat, feeding means for supplying paint to the internal surface of the tubular element and mechanicaldriying means for rotating the tubular element in an orbit about a center and for simultaneously causing rotation thereof about its own axis whereby paint" is centrifugally distributed within the element and is centrifugally thrown there- The pattern width was correspondingly less than in the i I revious examples or about six inches with other conditions same. g A

nis" understood that in order to obtain the full effect of distribntion, the centrifugal force applied within the emitters equal to or greater than the force tending to throwthe paint from the emitterthroats'. Other Wisc, the effect of rotation of the emitters about their longitudinal axes is substantially nullified.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

W at is c im d I l Q a 1 v c 1. In a paint spray apparatus, comprisingincombinationy a tubular spray head open at b oth ends thereof, supply means for supplying paint to the internal tubular surface of the spray head, and rotating driving means for simultaneously rotating the spray head in an orbit around a central point and for simultaneously mechanicallycausing rotation of said spray head; at a different speed about its axisjfor distributing the paint solely by the axial rotation thereof around the internal surface only of the tubular head and is substantially simultane; ously thrown outwardly centrifugally from opposite ends thereof solely 'by means of the orbital rotation thereof.

2. In a paint spray apparatus, comprising in combination; an elongated open tubular spray head, feeding means entering one end of said head for supplying fluid paint under suflicient pressure to cause paint flow onto the internal tubular surface of the spray head, rotating driving means for rotating the spray head about an orbit, and a second driving means dependent on said first mentioned driving means and rotating at a different speed for rotating the spray head about its longitudinal axis.

3. Ina paint spray apparatus, comprising in combinaan elongated open-ended tubular spray head, feedrnfeans entering one end of said head for supplying if (I paint under suflicient pressure to cause paint flow to the internal tubular surface of the spray head, mechanical driving means for rotating the spray head about an orbit, and a second driving means dependent on said first driving means for rotating the spray head about its longitudinal axis, said first and second mentioned driving means being proportioned so that each has an independent centrifugal action on the paint supplied to said spray head whereby the paint is dififibfii'itl upon the inner from arid is simultaneouslyel'cctrostatically dispersed as it passes from said element whereby thepaint is subseqnentl'ydeposit'ed on the axticle throug'h conjoint action of centrifugal and electrostatic forces. p

6. An electrostatic paint spray apparatus, a pair of tubular emitters aligned on a common longitudinal axis, means for rotating said emitters about their common longitud'inal axis, mechanical driving means" for simultaneously rotating said emitters about a second common axis positioned from the, longitudinal axis', paint supply means rotatable with said emitters about said second comrrion and stationary with respect to rotation about said corn'mon longitudinal axis for supplying paint to the internalsurfaces of said emitters, and" electrical means for establishing an electrostatic charge on said emitters;

"7. A paint spray apparatus, comprising in. combination; a support, a rotatable device mounted on said support, said device including a plurality of hcrizontally located radially outwardly extending tubular distributing elements, mechanical driving means fo rrotatin'g the device so that said elements are rotated about a common center, separate driving means for rotating said elements about their longitudinal axis which is displaced in aplane90 from the axis ,of rotation of said device, and feeding means for supplying paint to each of said elements adjacent the internal surface thereof whereby thepaint is centrifugally distributed by the rotational movement of said elements about their axes and is centriftiga'lly thrown outwardly of said elements by the over-all rotation of said device.

8. The paint spray apparatusclaimed in claim 7 wherein the feeding means cornp'rise a plurality of tubes connected to a rotatable cup open at the top thereof and a stationary paint supplyr tube for feeding paint into said cup whereby paint is supplied to the elements" solely by gravity. v V s 9. The paint spray apparatns as claimed in claim 7 wherein the mechanical driving means'comprises an electric motor and the separatedriving means comprises gearing operating between the stationary support and the elements.

References Cited in the file of this patent UNITED STATES'PATENTS Re; 19,374 Butterworth Nov. 20, 1934 2,484,577 Murphy Oct. 11, 1949 2,824,765 StangIe er al'. 1 Feb. 25, 1958 H FOREIGN PATENTS 741,313 Great Britain Nov. 30, 1955 

